Máximo J. Giglio

Histomorphometric study of bone healing around laminar implants in experimental diabetes.

The aim of this study was to evaluate the effects of experimental diabetes on the healing period leading to osseointegration. Wistar rats were injected with a single dose of streptozotocin (STZ); body weight and food intake were assessed every 48 hours. On days 2, 12, 26, and 42 post-STZ, glucemia, plasma hemoglobin, and urea were determined. Twelve days post-STZ, a titanium laminar implant was placed in the right tibia of each rat. Two groups of 20 rats each were killed on days 14 and 30 postimplantation, respectively. Results (ANOVA test) showed STZ-treated rats to have 1) a significant decrease in body weight; 2) an increase in food intake; 3) normal hemoglobin and plasma urea values; 4) a significant increase in glucemia; and 5) a decrease in tibiae length. Microscopic evaluation 14 days postimplantation revealed the presence of woven bone, and, at 30 days, laminar bone was in contact with the implant. Our findings show that, in this model of periimplant bone repair and under the experimental conditions stated herein, STZ-induced diabetes retards periimplant bone healing.

Effect of unilateral superior cervical ganglionectomy on mandibular incisor eruption rate in rats.

To assess the effect of sympathectomy on rat tooth eruption, the effect of a unilateral superior cervical ganglionectomy (SCGx) on eruption rate of ipsi- and contralateral lower incisors was examined. Two experiments were performed. In a first experiment, the eruption rate of ipsilaterally denervated incisors was similar to that of contralaterally innervated incisors, when assessed for up to 28 days after surgery. In a second experiment, under conditions of unilateral unimpeded eruption of incisors performed ipsilaterally or contralaterally to a unilateral SCGx, a significantly lower eruption rate of denervated incisors at the impeded eruption side, and a significantly higher eruption rate of denervated incisors at the unimpeded side were observed, when computed every 2 days. Significant differences in individual Students t tests at every time interval occurred mainly during the first and the last week of examination. When average daily eruption rate was computed in weekly intervals, a significant interaction between SCGx and the side of impeded or unimpeded eruption was found in a factorial ANOVA, that is, for each of the 4 weeks of examination, sympathetically denervated incisors showed lower eruption rates at the impeded eruption side, and higher eruption rates at the unimpeded side. These results indicate that incisor eruption is not modified by a local sympathetic denervation unless the contralateral lower rat incisor is cut out of occlusion.

Effects of cadmium on the function and structure of the rat salivary glands

The effects of sub-chronic cadmium (Cd) administration on the structure and subsequent secretory responses of the submaxillary and parotid glands to sialagogues were investigated. Female Wistar rats were injected subcutaneously with cadmium chloride (3.0 mg/kg body weight), 4 times a week for 2, 3 or 4 weeks. Functional and histopathological studies were done 3 days after the last injection. Dose-response curves for norepinephrine and methacholine were obtained. After 2 weeks of Cd administration significant changes in the secretory response to these sialogogues were observed. The dose-response curves after pretreatment with Cd for 3 weeks were also shifted to the right, but the response showed recovery when compared with that of 2-week treated animals. Parotid amylase concentration was also diminished by Cd. Treated rats had reduced acinar diameters, and an increase in acinar cell nuclei per field in both the submaxillary and parotid glands. Thus sub-chronic administration of ionized Cd produces morphological and functional changes in rat salivary glands. Moreover, the extent of tubular and acinar damage matches the degree of gland dysfunction as judged by the diminution of secretory responses to sialagogues.

Effects of chronic hypoxia on the secretory responses of rat salivary glands.

Female Wistar rats were placed for 3 weeks in a simulated chamber evacuated by a vacuum pump and maintained at 40.5 kPa (7100 m). Dose-response curves were obtained through the sequential injection, via the femoral vein, of increasing doses of methacholine, methoxamine, isoprenaline and substance P. The secretory activity in the parotid gland after exposure to chronic hypoxia was significantly decreased for all agonists studied, and the submaxillary gland showed the same behaviour except in relation to isoprenaline, which did not show a significant difference compared to controls. These data suggest that changes in the number or sensitivity of autonomic receptors and/or alterations in the intracellular signals caused by hypoxia may be involved in the reduction in salivary secretory responses.

Skeletal-unit growth in the mandible of rats given diphenylhydantoin

With the purpose of studying the effect of diphenylhydantoin on mandibular skeletal-unit growth, 28 male Wistar rats weighing 60.0 +/- 0.8 g were assigned to five different groups. One group received saline serving as normal controls; three others were injected intra peritoneally once daily with either 25, 50 or 100 mg/kg body wt diphenylhydantoin for 30 days; the fifth group was put on a restricted diet (20% below normal intake) for the same time. On day 31, the rats were killed by ether overdose and their mandibles were evaluated for differential skeletal-unit growth. Body-weight gain of diphenylhydantoin-injected rats was up to 24% less than controls, regardless of drug dose. Diet-restricted rats showed a similar difference. The amount of food consumed by diphenylhydantoin-injected rats was 21% less than that consumed by controls, regardless of drug doses. The concentration of alkaline phosphatase and haemoglobin in rats treated with 50 or 100 mg/kg diphenylhydantoin was lower than in controls and diet-restricted rats. However, plasma urea and total calcium were similar in diphenylhydantoin-treated rats and controls. Mean appetite quotient, and the efficiency of protein and energy utilization, did not appear to change in response to the particular diphenylhydantoin dose or to the restricted diet. Mandibular dimensions of rats injected with 25 or 50 mg/kg diphenylhydantoin were not statistically different from those of the control and diet-restricted groups. With using 100 mg/kg diphenylhydantoin for 30 days, the growth of symphysial and basal heights, condylar and angular lengths and condylar width was significantly less than in the control and diet-restricted groups. The remaining mandibular skeletal units did not exhibit significant differences from those of control and diet-restricted rats. The disharmonious growth of the mandible does not appear to depend on suboptimal energy intake, efficiency of protein-energy utilization, renal failure and anaemia, but would suggest a differential toxicological effect of diphenylhydantoin on the osseous component and/or its associated non-skeletal tissues.

Influence of bisphosphonate on the negative erythropoietic effects of uranyl nitrate

Uranium salts, such as uranyl nitrate, induce severe renal dysfunction and tubular necrosis and a significant impairment of both oxygen dependent erythropoietin production and response to recombinant human erythropoietin. All effects are transient and reach maximal severity on the 7th day post injection. We investigated the effects of ethane 1-hydroxy-1,1-bisphosphonate, which counteracts the inhibitory effect of uranyl nitrate on bone formation, on the negative erythropoietic effects of uranyl nitrate. Adult female Wistar rats received 1 mg/kg body weight of uranyl acetate by the i.v. route. Ethane 1-hydroxy-1,1-bisphosphonate was injected simultaneously at a dose of 7.5 mg/kg by the same route. Seven days after drug injections, plasma erythropoietin was estimated after hypobaric hypoxemia or cobalt chloride administration. The response to exogenous erythropoietin was also measured in uranyl nitrate- and/or ethane l-hydroxy-l,l-bisphosphonate-injected rats made polycythemic by transfusion. The erythroid response was quantitated in terms of red blood cell59iron uptake. Ethane 1-hydroxy-1,1-bisphosphonate counteracted the effect of uranyl nitrate on oxygen-dependent and cobalt-dependent erythropoietin production, but did not correct the right shift of the dose-response relationship for exogenous erythropoietin induced by uranyl nitrate in the polycythemic rat.